chem paper june definitions

Define reduction

The gain of electrons

Define molar mass

the mass in grams of one mole of that substance

What is concentration

The amount of solute per unit volume solution

What is an intramolecular bond?

A bond between atoms within molecules

What is a intermolecular bond?

Force of attraction between molecules or atoms of noble gasses

Define electronegativity?

The measure of tendency of an atom to attract a bonding pair of electrons

What is heat of reaction

The net change of chemical potential energy of the system

What is activation energy

The minimum amount of energy required to start a chemical reaction

What is the activated complex

The high energy unstable transition state between the reactants and products

Define reaction rate

The change in the amount of concentration per unit time of either a reactant or product

Define a catalyst

A substance that increases the rate of the reaction but remains unchanged at the end of the reaction

define a closed system

A system in which mass is conserved inside the system but energy can enter or leave the system freely

Define an open system

A system in which matter and energy can be exchanged between the system and its surroundings

State me chatelier principle

When an external stress is applied to a system in dynamic chemical equilibrium the equilibrium point will change in such a way to counteract the stress

Define oxidation

The loss of electrons

Define redox reaction

Reaction involving the transfer of electrons

Define anode?

The electrode where oxidation takes place

Define cathode

The electrode where reduction takes place

What is a galvanic cell?

An electrochemical cell that converts the chemical energy of spontaneous redox reactions into electrical energy

What is the oxidizing agent?

The substance that accepts electrons (think opposites for the agents)

What is the reducing agent?

The substance that donates electrons

Define limiting reagent

Limiting reagent in a reaction is the reactant that is consumed completely. It determines the maximum amount of product that is made.

What is percentage yield

Percentage yield is a measure of the extent of a reaction determined by comparing the actual amount to the theoretical amount of product expressed as a percentage.

Cathode

The electrode where reduction takes place

define an electrolyte

A substance that can conduct electricity due to the presence of free ions when molten or dissolved in solution

Define an acid

An acid is defined as a proton donor

Define a base

A base is defined as a proton acceptor

What is ionization

The reaction of a molecular substance with water to produce ions

Define a strong acid

An acid that ionises almost completely in an aqueous solution

Define a weak acid

A weak acid is an acid that ionises only partially in an aqueous solution

Define a strong base

A base that dissociates almost completely in an aqueous solution

Define a weak base

A base that only ionizes partially in an aqueous solution

Define dissociation

The splitting of an ionic compound into its ions

What are some weak acids names and formula?

HF hydrofluoric acid, H3PO4 phosphoric acid,

Define an endothermic reaction

reactions which transform thermal energy into chemical potential energy

define exothermic reaction

Reactions which transform chemical potential energy into thermal energy

What are some examples of ampholytic/amphoteric substances

H20, HCO3

Define an amphoteric substance

A substance that can act as either an acid or a base

Define a salt

A substance in which the hydrogen of an acid has been replaced by a cation

Define the hydrolysis of a salt

The reaction of an ion with water

Define neutralization

A chemical reaction in which an acid and a

base react so that neither is in excess

What is a standard solution

A solution of known concentration

Defined activation energy

The minimum amount of energy needed for a reaction to take place

Define activated complex

high energy unstable state between products and reactants

What is a a catalyst

A substance that increases the rate of a chemical reaction without itself undergoing a permanent change in the reaction

Define heat of reaction

the net change of chemical potential energy of the system

Define an ampholyte

Substance that can act as either acid or base is amphiprotic or ampholyte

What is the formula for sulphuric acid and is it a strong or weak acid ?

H2SO4 it is a strong acid

what is the formula for oxalic acid and is it strong or weak base

(COOH)2 it is a weak acid

Is sodium hydroxide a strong or weak base

NaOH is a strong base

Is calcium hydroxide a strong or weak base

CaOH2 is a strong base

Is ammonia a strong or weak base

NH3 Weak base

Define a salt?

A substance in which the hydrogen of an acid has been replaced by a cation

What is hydrolysis of a salt

the reaction of an ion from a salt with water

define a hydrocarbon

A compound containing only carbon and hydrogen atoms

Define a saturated compound

A compound in which all of the bonds between carbon atoms are single bonds.

Define unsaturated compound

A compound in which there is atleast one double and or triple bond between carbon atoms

Define a functional group

An atom or group of atoms that form the center of chemical activity in the molecule

Define a homologous series

A series of similar compounds which has the same functional group and same general formula in which each member differs from the previous one by a single ch2 unit

Define a structural isomer

Compounds that have the same molecular formula but different structural formula

What is an electrolyte?

The substance that can conduct electricity due to the presence of free (mobile) ions when molten or dissolved in aqueous solution.

What is electrolysis

The process whereby a chemical change os produced in an electrolyte by an electric current

What does the reaction of an acid and a metal form?

A salt and H2 gas

What does the reaction of an acid and metal oxide form?

A salt and water

What does the reaction of an acid and metal hydroxide form

A want and water

What does the reaction of a salt and metal carbonate form?

Salt and water and co2 gas

Define a standard solution?

Solution of known concentration

What indicator will a titration between a strong acid and weak base need?

Methyl orange. (Acidic ranges 0-6)

What indicator will a titration between a strong acid and strong base or weak acid and weak base be?

Bromothymol blue (neutral point 7)

What indicator will a titration between a strong base and weak acid need?

Phenolphthalein (basic ranges 7-10)

What does the reaction of an acid and ammonia form?

Ammonium salt eg NH4Cl

What is metallic bonding?

The attraction between positive kernels and a sea of deli delocalised electrons

What is ionic bonding?

The transfer of electrons to form cations and anions which are electrostatically attracted in a crystal lattice

What is a covalent bond?

The sharing of atleast one pair of electrons by two atoms

Why is hydrogen bonding so strong?

They bond with N,O,F atoms which have a large electronegativity and have a lone pair of electrons. When bonding with the hydrogen they pull the electron pair away from the H because of high EN. This in turn creates a strong dipole.

What two things are needed for a collision to be considered effective?

The orientation of the particles and the particles must have a sufficient kinetic energy (bigger than or equal to the activation energy) so that it can overcome the forces of repulsion and bond

how does temperature affect the rate of the reaction in terms of collision theory?

the particles will have a higher average kinetic energy

More particles will have a kinetic energy that is greater than or equal to the activation energy

This means there will be more effective collisions per unit time

The rate of reaction increases

How does using a powder form over a tablet form increase rate of reaction?

the surface area will be larger meaning there will be more collisions per unit time.

This increases the number of effective collisions per unit time

Which increases the reaction rate

how does concentration increase reaction rate with collision theory?

When there is a higher concentration there is a larger number of particles.

This means more particles having kinetic energy that is equal or greater to the activation energy

Which means more collisions per unit time

Which means more effective collisions per unit time

How does pressure increase reaction rate in terms of collision theory?

When the pressure is higher or the volume becomes smaller the particles are closer together which means that there will be more collisions per unit time which means more effective collisions per unit time which increases the rate of reaction

how does a catalyst increase the rate of a reaction in terms of collision theory

Catalysts decrease the activation energy for a reaction so more particles will meet the threshold and have an ek that is greater than or equal to the activation energy which means more effective collisions per unit time

How is London forces formed?

The electron cloud may become unevenly distributed which induces a temporary dipole. oppositely charged dipoles of each molecule are attracted to each other